International Mirror Class Association of Tasmania.
UK MCA PROPOSALS FOR BERMUDA RIG AND ALLOY BOOM
Part B Rule 5.2 Main Boom.
It is proposed that aluminium alloy is permitted as an alternative to wood and that Rule 5.2 be amended as follows:
Rule 5.2.1 The overall length of the boom, excluding fittings and end-plugs shall be 2260mm ±25mm.
Rule 5.2.2 The boom shall be either of solid unlaminated wood or of aluminium alloy extrusion (90+% Aluminium) with integral tracks. End-plugs of any material may be fitted.
Rule 5.2.3 Except within 100mm of its forward end the wood boom shall be of constant section of 40mm ±3mm depth and 40mm ±3mm width. The aluminium alloy boom shall be of constant section throughout its length and with all fittings removed be able to pass through a circle of 53mm diameter.
Rule 5.2.4 The distance from the inner end of the boom to the opposite side of the kicking strap block in the case of the wooden boom or to the effective point of attachment of the kicking strap for the aluminium alloy boom, shall be not less than 483mm.
Rule 5.2.5 No fitting shall be attached to the side of the boom aft of the kicking strap attachment point. Any point on the cross section where a tangent to the surface is inclined at more than 45 degrees to the horizontal shall be considered as forming the side of the boom. The aluminium alloy boom may not be rigged internally.
Rule 5.2.6 A clew outhaul track may be recessed flush to the top of the wood boom.
Part B Rule 5 Spars
It is proposed that an aluminium alloy Bermuda mast be permitted as an option and alternative to the existing gunter mast and gaff defined in Rules 5.1 & 5.3 and that the following changes to Rule 5 be made:
Insert new paragraph after 5. SPARS Boats may have a gunter rig, comprising a gunter mast and a gaff, or a Bermuda rig, comprising a Bermuda mast. Only one of these rig configurations may be used in any one event of less than 14 consecutive days duration.
Rule 5.1 Gunter Mast
Rule 5.5 Bermuda Mast
Rule 5.5.1 Measurements shall be taken according to the ISAF Equipment Rules of Sailing 2005-2008 (ER) unless specified. When a term is used in its defined sense, it is printed in “italic” type if defined in the ISAF Racing Rules of Sailing (RSS) and in “bold” type if defined in the ER.
Rule 5.5.2 The spar shall be of aluminium alloy extrusion (90+% Aluminium)
Rule 5.5.3 The spar shall include a fixed sail groove or track which may or may not be integral with the spar. Sail grooves and tracks which are not part of the spar extrusion may be of aluminium alloy extrusion (90+% aluminium) or plastic.
Rule 5.5.4 The spar may be capable of being disassembled into two pieces. The method of joining a two piece spar is optional.
Rule 5.5.5 With the exception of the heel fitting, the spar shall be of constant section below the shroud rigging point.
Rule 5.5.6 The spar with all fittings removed shall be able to pass through a 70mm diameter circle.
Rule 5.5.7 The aft side of the spar shall be straight. The greatest distance between the spar and a straight line between the upper point and the lowest point on the aft face of the spar is 30mm.
Rule 5.5.8 The main halyard may pass internally through the spar. No other halyard or control line may be rigged inside the spar.
Rule 5.5.9 Spreaders, diamond stays and similar contrivances are not permitted.
Rule 5.5.10 It shall not be possible for the spar to move in the mast step by more than 2mm in any direction when the mast is raised.
Rule 5.5.11 The mast datum point is the point on the front face of the spar 100mm above the top surface of the foredeck butt strap with the mast raised on the mast step.
Rule 5.5.12 Dimensions Minimum Maximum
Mast limit mark width 16mm
Upper point height 4757mm
Forestay height 3165mm
Shroud height 3165mm
Spinnaker host height 3183mm
Spinnaker pole fitting projection 35mm
Mast datum point to the top of the main boom spar 559mm 579mm
Part B other rules
Some other rules will need to be changed to accommodate the Bermuda rig. These are as follows:
Rule 1.6.13 The material of the mast step is optional.
Rule 126.96.36.199 For boats equipped with a gunter rig the following shall apply. The top surface of the mast step shall be no more than 12mm above the top surface of the foredeck butt strap. The centre of the mast step shall be 2160mm ± 15mm forward of the forward face of the aft transom at deck level. A drain hole not exceeding 6mm diameter is permitted in the mast step.
Rule 188.8.131.52 For boats equipped with a Bermuda rig the following shall apply. The design of the mast step is optional and may include a hinging heel mechanism to aid stepping the mast. The centre of the mast spar at its lowest point shall be 2160mm ± 15mm forward of the forward face of the aft transom.
Rule 184.108.40.206 An optional second mast step may be fitted outside of the above tolerances but shall not be used while racing.
Rule 6.1.1 Only the following standing rigging of wire rope not less than 2mm diameter shall be fitted:
Two shrouds } A plastic or GRP cap to protect the
One jib halyard strop } gunter mast from rigging is permitted
Rule 6.1.2 All standing rigging shall be attached to the gunter mast by being looped over the top of the mast not more than 50mm from its top. The method of attaching the standing rigging to the Bermuda mast spar is optional.
Rule 220.127.116.11 There may be a maximum of 6 luff lacing eyesbelow the LMP.Rule 7.6.3 The mainsail shall be set so that the highest visible point at the head is lower than the lower edge ofthe gaff measurement band, or the Bermuda mast upper point